You need two Postcard stamps if those are the only stamps you use on a standard one-ounce domestic letter. At current rates, one Postcard stamp is worth 65¢, while the letter needs 82¢. Two total $1.30 and overpay by 48¢.
Current Value Comparison
| 1 Postcard stamp | 65¢ | 17¢ short |
|---|---|---|
| 2 Postcard stamps | $1.30 | Enough, but 48¢ overpaid |
| 1 ordinary Forever stamp | 82¢ | Exact base letter value |
The Lower-Cost Combination
If you have other valid postage, use one Postcard stamp plus at least 17¢ in additional denomination stamps:
65¢ + 17¢ = 82¢
If you do not have the exact 17¢, combine stamps until the total reaches or exceeds 82¢. USPS accepts valid postage combinations, but routine overpayment is not refunded after mailing.
Why One Postcard Stamp Is Not Enough
A nondenominated stamp marked “POSTCARD” tracks the current domestic postcard price. It does not automatically become equal to the ordinary Forever one-ounce letter price. A letter in an envelope uses the letter category even if the paper inside is a postcard or greeting card.
When Two Postcard Stamps Still May Not Be Enough
The $1.30 total is enough for many ordinary one-ounce letters, but the mailpiece itself controls the requirement. More postage can be needed when it is:
- heavier than one ounce;
- square, rigid or nonmachinable;
- too large or thick for letter dimensions;
- sent internationally; or
- mailed with an extra service.
Measure and weigh the finished envelope, including inserts and decorations.
Postcard Stamp vs. Ordinary Forever Stamp
| Stamp marking | Value follows | Typical use |
|---|---|---|
| POSTCARD | Current domestic postcard rate | Qualifying standard postcard |
| FOREVER | Current one-ounce First-Class Mail letter rate | Qualifying one-ounce domestic letter |
Both can remain valid as nondenominated postage, but they follow different price categories.
Frequently Asked Questions
Can Postcard stamps be used on envelopes?
Yes. They contribute their current postage value, but one does not currently pay the full one-ounce letter rate.
Will two Postcard stamps mail a one-ounce letter?
Yes, provided the letter otherwise qualifies. The combination currently overpays by 48¢.
Can I use one Postcard stamp and a 17-cent stamp?
Yes. That combination currently totals the 82¢ base letter price.
Do old nondenominated Postcard stamps keep their value?
Genuine, unused stamps marked POSTCARD continue to track the current domestic postcard category, not their original purchase price.
Official Sources
See USPS guidance for domestic letters and postcards and the rules for nondenominated postage.
Rates checked September 1, 2026.